5
MAN3038-2
DISCOVERY PRODUCT GUIDE
5
Optical Smoke Detector
5.1
Operating Principles:
The Discovery Optical Detector has a white moulded polycarbonate
case with wind-resistant smoke inlets. The indicator LEDs are
colourless when the detector is in quiescent state and red in alarm.
Within the case is a printed circuit board which, on one side, has the
light-proof chamber with integral gauze surrounding the optical
measuring system and, on the other, the signal processing and
communications electronics.
An infra-red light emitting diode within its collimator is arranged at
an obtuse angle to the photo-diode. The photo-diode has an integral
daylight-blocking filter. The IR LED emits a burst of collimated light
every second. In clear air the photodiode receives no light directly from the IR LED, because of the angular
arrangement and the chamber baffles. When smoke enters the chamber it scatters light from the emitter IR
LED onto the photo-diode in an amount related to the smoke characteristics and density. The photodiode
signal is processed to provide an analogue value for transmission when the detector is interrogated.
Mode
Alarm threshold %/m
dB/m
Minimum time to alarm
(sec)
1
1.4
0.06
5
2
1.4
0.06
30
3
2.1
0.09
5
4
2.1
0.09
30
5
2.4
0.11
5
Table 1 – Optical Detector Operating Modes (rates comply with EN54-7: 2000)
Figure 2 - Top Section - Discovery Optical Smoke Detector
5.2
Product Codes
Product Description
EN54-7
AS7240-7
Discovery Optical Smoke Detector
58000-600AMP
4106-2005
